1. Field of the Invention
This application relates generally to steering columns, and more specifically, to adaptive energy absorbing devices for collapsible steering columns.
2. Description of the Related Art
Automotive steering columns are typically equipped with kinetic energy absorption devices. The energy absorption devices reduce injury to a vehicle operator caused by the operator impacting a steering wheel as a result of a collision event. Such impacts during vehicle collision typically cause the steering column to collapse. The energy absorption devices absorb the energy transmitted through the steering column as the steering column collapses.
Such energy absorbing steering columns generally include a housing that translates linearly through a collapse stroke during the collision event. A force generated by the driver impacting the steering wheel initiates the collapse stroke. The steering wheel housing moves against a resisting or reactive force that may be produced by an energy absorption device designed to convert a portion of the driver's kinetic energy into work. The resisting force may be generated by systems including a plastically deformable metal element that is a part of the energy absorbing device. Such energy absorbing devices have fixed energy absorption capabilities, and offer no control over their performance during the collapse stroke. More specifically, traditional energy absorbing devices have a fixed energy absorbing curve which is optimized to protect a given and limited group of drivers. In most cases the group represents an average size male driver.
In order to provide a variable energy absorption curve, pyrotechnic devices have been incorporated into the collapsible steering column assembly to selectively engage any number of a plurality of energy absorption devices disposed on the steering column assembly. Such a steering column assembly is disclosed in U.S. Pat. No. 6,578,872 to Duval et al. Steering column assemblies including the pyrotechnic devices allow the energy absorption curve to be customized to match attributes of the driver, and the severity of the collision event. However, variability of the energy absorption curve is based on engaging zero, one, two, etc energy absorption devices disposed on the steering column assembly. The amount of energy absorbed by each individual energy absorption device does not vary.